THE NATIONAL GEOGRAPHIC MAGAZINE
Photograph by Joseph S. McCoy, Jr.
HOMEMADE TELESCOPES REVEAL THE HEAVENS TO AMATEUR ASTRONOMERS
The 6-inch reflecting telescopes were made by these men who are members of the National
Capital Amateur Astronomers Association of Washington, D. C. They ground the mirrors, and
most of the tubes are of sheet metal. The image of a star, planet, or the Moon is reflected from a
large mirror to a prism and thence to the eyepiece in the side where the observer sees it.
travels two million years before it reaches
the nearest neighboring galaxy.
In the midst of one of these galaxies
one of the flatter, thinner ones-is a yellow
star, smaller than the average, just one
among 30,000 million other stars in the
galaxy. It happens to be our Sun. Circling
around it are comets, asteroids, clouds of
dust, and nine planets. One of the smaller
of these planets is the little Earth on which
we ride (Color Plate I).
This tiny globe of rock and iron, only
8,000 miles thick, is a mere speck in one
great galaxy of stars. Yet, so far as we
now know, it is the only place in explored
space where intelligent life exists.
VAST KNOWLEDGE FROM MERE RAYS
OF LIGHT
But though man must stay forever tied
to the career of a single unimportant star,
his mind is not so restricted. From the
tiny one-celled organisms that were the be
ginnings of life on Earth has developed an
intelligence that can explore a billion times
six trillion miles out into the Universe.
And the mind of man has done all this
with but a single tool, the rays of light.
Except for a few facts gleaned from mete
orites, we have gained our whole vast knowl
edge of the Universe from light, and light
alone (Color Plate VII).
Just what light is, no one can surely
say. But we do know that when it is split
up into its different colors, or wave lengths,
each wave length vibrates a different num
ber of times per second, like the different
notes on the piano. And each of the 92
elements of which the Universe is made
will, when in a gaseous state, radiate or ab
sorb light of different colors or wave lengths,
an identification as positive and individual
as a fingerprint.
So, taking the light of a distant star, we
can split it into its different wave lengths,
and they tell us positively that there are
in that star, for example, oxygen, helium,
hydrogen, sodium, or other familiar things.
Moreover, we can photograph the spec
trum, or split-up light of a star, and the
resulting picture shows a series of lines,
arranged like the rungs of a ladder. From